EP0250308A1 - Plasma torch for powder spraying - Google Patents

Plasma torch for powder spraying Download PDF

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Publication number
EP0250308A1
EP0250308A1 EP87401339A EP87401339A EP0250308A1 EP 0250308 A1 EP0250308 A1 EP 0250308A1 EP 87401339 A EP87401339 A EP 87401339A EP 87401339 A EP87401339 A EP 87401339A EP 0250308 A1 EP0250308 A1 EP 0250308A1
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EP
European Patent Office
Prior art keywords
anode
plasma
outlet orifice
axis
cathode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87401339A
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German (de)
French (fr)
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EP0250308B1 (en
Inventor
Claude Mouchet
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NOUVELLE DE METALLISATION INDUSTRIES SNMI Ste
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NOUVELLE DE METALLISATION INDUSTRIES SNMI Ste
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Priority to AT87401339T priority Critical patent/ATE56343T1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/16—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed
    • B05B7/22—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc
    • B05B7/222—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc using an arc
    • B05B7/226—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc using an arc the material being originally a particulate material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3478—Geometrical details
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder, liquid

Definitions

  • the invention relates to a plasma recharging torch and in particular a torch of the transferred plasma type.
  • FIGS. 1a and 1b respectively show in longitudinal section and at the end of the end of a transferred plasma recharging torch illustrating the state of the art.
  • This torch which generally has a symmetry of revolution about an axis XX ⁇ , comprises a central cathode 10 and an annular anode 12 surrounding this cathode.
  • the cathode 10 generally made of tungsten, has the shape of a cylindrical rod terminated by a tapered end 10a, of conical shape.
  • the anode 12 generally made of copper, has a cylindrical recess 13 in which the cathode 10 is received.
  • An annular space 14 formed between the cathode and the anode makes it possible to inject a plasma gas, as indicated by the arrows F1 on Figure 1a.
  • the cylindrical recess 13 formed in the anode 12 extends beyond the tip of the tapered end 10a of the cathode by a portion of reduced diameter delimiting an outlet orifice 15 for the plasma gas.
  • This outlet orifice 15 opens onto the planar end face 16 of the anode 12. This face is perpendicular to the axis XX ⁇ of the torch and also constitutes the end of the latter.
  • the plasma gas introduced according to the arrows F1 is ionized to form a plasma P.
  • this plasma P is confined in the orifice 15 and can escape only through the open end of the latter.
  • the transfer of plasma between the torch and the substrate to be recharged (not shown in Figure 1) is obtained by creating a potential difference between the torch and the substrate.
  • two channels 20 formed in the anode 12 symmetrically with respect to the axis XX ⁇ make it possible to introduce into the plasma P leaving the torch a recharging powder.
  • the channels 20 generally extend in a direction parallel to the axis XX ⁇ and have, at the outlet orifice 15, ends 20a inclined towards this axis XX ⁇ , in order to direct the recharging powder towards the plasma P, like the 'illustrate the arrows F2 in Figure 1a.
  • the transfer of the powder to the planar end face 16 of the cathode is carried out by means of a carrier gas.
  • the channels 20 are replaced by an annular chamber formed in the anode and whose part opening onto the end face of the anode is directed towards the axis of the torch, to present approximately the shape of a funnel.
  • the powder / carrier gas mixture is then injected tangentially to the wall of the annular chamber, so that it travels in this chamber along an approximately helical path, to the plasma leaving the torch.
  • part of the recharging powder is not transferred by the plasma to the substrate to ensure recharging.
  • part of the powder is lost and especially that this powder tends to dust the machine, which leads to risks of seizing thereof and complicates maintenance operations.
  • the present invention specifically relates to a plasma torch generally operating in a manner similar to existing torches, while not having the aforementioned drawbacks.
  • the invention relates to a plasma torch allowing an improvement in the heat exchanges between the powder and the plasma and creating a gaseous curtain around the plasma ensuring the transfer of the powder, so as to reduce the deterioration of the electrodes, to reduce the power consumption, to protect the molten powder conveyed by the plasma and the liquid bath formed on the substrate against oxidation, and to avoid the propagation of grains of powder outside the recharging zone.
  • a plasma recharging torch comprising, along a common axis, a central cathode having a tapered end, and an annular anode surrounding the cathode and delimiting therewith a space extending beyond the tapered end of the cathode by an outlet orifice formed in the anode, at least one inlet passage for recharging powder being formed in the anode and having at one end of said outlet orifice outlet inclined towards said axis, characterized in that the outlet orifice has a rear part adjacent to the annular space and a front part opening out and of diameter greater than the diameter of the rear part, the inclined end of the recharging powder inlet passage opening into the front part of the outlet orifice, channels substantially parallel to said axis being formed in the anode around the rear part of the outlet orifice, to communicate the front part of this orifice with said annular space.
  • this torch comprises at least six channels distributed around its axis.
  • the torch also comprises two powder inlet passages arranged symmetrically with respect to its axis.
  • the transferred plasma recharging torch shown in FIGS. 2a and 2b has a structure close to the structure of the torch according to the prior art described previously with reference to FIGS. 1a and 1b. For this reason, the same reference numbers increased by one hundred are used to designate similar elements.
  • the torch according to the invention comprises a central cathode 110 and an annular anode 112 both arranged along a common axis XX ⁇ .
  • the cathode 110 for example made of tungsten, has the shape of a cylindrical rod terminated by a tapered end 110a of conical shape.
  • the anode 112 has a cylindrical bore 113 in which is housed the cathode 110 and delimiting with the latter an annular space 114.
  • This space 114 is used to inject the plasma gas, constituted in a known manner either by argon or by an argon-hydrogen, helium-hydrogen, nitrogen- mixture hydrogen, nitrogen-helium, etc ...
  • the cylindrical bore 113 formed in the anode 112 extends beyond the tip of the tapered end 110a of the cathode, in the form of an outlet orifice 115 opening onto the flat end face 116 of the 'anode.
  • This face 116 perpendicular to the axis XX ⁇ , also forms the end of the torch.
  • the outlet orifice 115 comprises a rear part 115a connected to the bore 113 by a part having a circular arc section and a front part 115b opening onto the end face. 116.
  • the diameter of the front part 115b is slightly greater than the diameter of the rear part 115a, these two parts being separated by a straight shoulder.
  • channels 122 extending parallel to the axis XX ⁇ are formed in the anode 112, around the rear part 115a of the outlet orifice, so as to directly communicate the annular space 114 with the part before 115b of the outlet.
  • these channels 122 are six in number, distributed around the axis XX ⁇ .
  • the recharging powder mixed with the carrier gas reaches the end of the torch by two passages 120 arranged symmetrically with respect to the axis XX ⁇ .
  • These passages 120 which extend substantially parallel to this axis XX ⁇ , have at the outlet orifice 115 ends 120a inclined towards the axis XX ⁇ and opening out according to the invention in the front part 115b of this orifice.
  • the plasma recharging torch according to the invention operates in the following manner.
  • the plasma gas admitted by the annular space 114 (arrows F1) is ionized to form a plasma P in the outlet orifice 115, beyond the tip of the tapered end 110a of the cathode.
  • the plasma P is transferred to the substrate by escaping through the orifice 115.
  • the recharging powder conveyed by the carrier gas in the passages 120 (arrows F2) is injected directly into the plasma P.
  • This injection takes place in a confined area and not at the beyond the end of the torch as in the prior art, the heat exchanges between the powder and the plasma are improved. This results in less deterioration of the electrodes, a reduction in the power to be used and, consequently, a significant saving.
  • This gaseous curtain limits the spread of powder grains outside the recharging area. This results in an increase in the yield of the powder as well as less dust from the machines. The risks of seizure of these are reduced, as well as maintenance work.
  • the gaseous annular curtain obtained thanks to the channels 122 makes it possible to better protect the molten powder entrained by the plasma P from oxidation, as well as the liquid bath formed on the substrate.
  • this same gaseous curtain provides thermal protection for the wall of the front part 115b of the outlet orifice and also reduces the risk of catching molten powder on this same wall near the end face 116. By Consequently, the resistance over time of the anode 112 is not penalized by the lengthening of its end required by the injection of the recharging powder in a confined area.
  • the injection of the recharging powder can be done by an annular passage in which the powder circulates according to a helical trajectory.
  • the number and the shape of the channels 122 can be modified, these channels being able for example to present in section the shape of arcs of a circle.
  • the arrangements usually fitted to plasma recharging torches and which have not been described for simplicity can of course be provided on the torch according to the invention.
  • means for cooling the electrodes, and in particular the anode, generally consisting of a circulation of a fluid such as water can be provided.
  • the invention is particularly suitable for a reloading torch with transferred plasma, it can also be applied to a blown plasma torch.

Abstract

1. Plasma torch for resurfacing comprising, along a common axis (XX'), a central cathode (110) having a tapered end (110a) and an annular anode (112) surrounding the cathode and delimiting therewith an annular space (114) for the supply of plasma-producing gas, this space being extended beyond the tapered end of the cathode by an outlet orifice (115) formed in the anode, at least one passage (120) for the supply of resurfacing powder being formed in the anode and having, at the level of the said outlet orifice, an outlet end (120a) tilted towards the said axis, characterized in that the outlet orifice (115) has a rear part (115a) adjacent to the annular space (114) and a front part (115b) emerging outside and having a diameter greater than the diameter of the rear part, the tilted end (120a) of the passage for the supply of resurfacing powder emerging in the front part (115b) of the outlet orifice, channels (122), substantially parallel to the said axis (XX'), being formed in the anode (112), around the rear part (115a) of the outlet orifice, in order to place the front part (115b) of this orifice in communication with the said annular space (114).

Description

L'invention concerne une torche de rechargement à plasma et notamment une torche du type à plasma transféré.The invention relates to a plasma recharging torch and in particular a torch of the transferred plasma type.

Les figures 1a et 1b représentent respectivement en coupe longitudinale et en bout l'extrémité d'une torche de rechargement à plasma transféré illustrant l'état de la technique.FIGS. 1a and 1b respectively show in longitudinal section and at the end of the end of a transferred plasma recharging torch illustrating the state of the art.

Cette torche, qui présente généralement une symétrie de révolution autour d'un axe XXʹ, comprend une cathode centrale 10 et une anode annulaire 12 entourant cette cathode.This torch, which generally has a symmetry of revolution about an axis XXʹ, comprises a central cathode 10 and an annular anode 12 surrounding this cathode.

De façon plus précise, la cathode 10, généralement en tungstène, a la forme d'une tige cylindrique terminée par une extrémité effilée 10a, de forme conique. L'anode 12, généralement en cuivre, présente un évidement cylindrique 13 dans lequel est reçue la cathode 10. Un espace annulaire 14 ménagé entre la cathode et l'anode permet d'injecter un gaz plasmagène, comme l'indiquent les flèches F₁ sur la figure 1a.More specifically, the cathode 10, generally made of tungsten, has the shape of a cylindrical rod terminated by a tapered end 10a, of conical shape. The anode 12, generally made of copper, has a cylindrical recess 13 in which the cathode 10 is received. An annular space 14 formed between the cathode and the anode makes it possible to inject a plasma gas, as indicated by the arrows F₁ on Figure 1a.

L'évidement cylindrique 13 formé dans l'anode 12 se prolonge au-delà de la pointe de l'extrémité effilée 10a de la cathode par une partie de diamètre réduit délimitant un orifice de sortie 15 pour le gaz plasmagène. Cet orifice de sortie 15 débouche sur la face d'extrémité plane 16 de l'anode 12. Cette face est perpendiculaire à l'axe XXʹ de la torche et constitue également l'extrémité de celle-ci.The cylindrical recess 13 formed in the anode 12 extends beyond the tip of the tapered end 10a of the cathode by a portion of reduced diameter delimiting an outlet orifice 15 for the plasma gas. This outlet orifice 15 opens onto the planar end face 16 of the anode 12. This face is perpendicular to the axis XXʹ of the torch and also constitutes the end of the latter.

Lors de l'établissement d'une tension électrique entre la cathode 10 et l'anode 12, le gaz plasmagène introduit selon les flèches F₁ est ionisé pour former un plasma P. Compte tenu de la forme de l'extrémité effilée 10a de la cathode et du diamètre réduit de l'orifice de sortie 15, ce plasma P est confiné dans l'orifice 15 et ne peut s'échapper que par l'extrémité ouverte de celui-ci. Le transfert du plasma entre la torche et le substrat à recharger (non représenté sur la figure 1) est obtenu en créant une différence de potentiel entre la torche et le substrat.When establishing an electrical voltage between the cathode 10 and the anode 12, the plasma gas introduced according to the arrows F₁ is ionized to form a plasma P. Taking into account the shape of the tapered end 10a of the cathode and of the reduced diameter of the outlet orifice 15, this plasma P is confined in the orifice 15 and can escape only through the open end of the latter. The transfer of plasma between the torch and the substrate to be recharged (not shown in Figure 1) is obtained by creating a potential difference between the torch and the substrate.

Par ailleurs, deux canaux 20 formés dans l'anode 12 de façon symétrique par rapport à l'axe XXʹ permettent d'introduire dans le plasma P sortant de la torche une poudre de rechargement. Les canaux 20 s'étendent généralement selon une direction parallèle à l'axe XXʹ et présentent au niveau de l'orifice de sortie 15 des extrémités 20a inclinées vers cet axe XXʹ, afin de diriger la poudre de rechargement vers le plasma P, comme l'illustrent les flèches F₂ sur la figure 1a. Le transfert de la poudre jusqu'à la face d'extrémité plane 16 de la cathode est réalisé au moyen d'un gaz porteur.Furthermore, two channels 20 formed in the anode 12 symmetrically with respect to the axis XXʹ make it possible to introduce into the plasma P leaving the torch a recharging powder. The channels 20 generally extend in a direction parallel to the axis XXʹ and have, at the outlet orifice 15, ends 20a inclined towards this axis XXʹ, in order to direct the recharging powder towards the plasma P, like the 'illustrate the arrows F₂ in Figure 1a. The transfer of the powder to the planar end face 16 of the cathode is carried out by means of a carrier gas.

On connaît également des torches à plasma transféré présentant une structure légèrement différente de celle qui vient d'être décrite en se référant aux figures 1a et 1b.Also known are transferred plasma torches having a structure slightly different from that which has just been described with reference to FIGS. 1a and 1b.

Ainsi, dans certaines torches connues, les canaux 20 sont remplacés par une chambre annulaire formée dans l'anode et dont la partie débouchant sur la face d'extrémité de l'anode est dirigée vers l'axe de la torche, pour présenter approximativement la forme d'un entonnoir. Le mélange poudre/gaz porteur est alors injecté tangentiellement à la paroi de la chambre annulaire, de sorte qu'il chemine dans cette chambre selon une trajectoire approximativement en hélice, jusqu'au plasma sortant de la torche.Thus, in certain known torches, the channels 20 are replaced by an annular chamber formed in the anode and whose part opening onto the end face of the anode is directed towards the axis of the torch, to present approximately the shape of a funnel. The powder / carrier gas mixture is then injected tangentially to the wall of the annular chamber, so that it travels in this chamber along an approximately helical path, to the plasma leaving the torch.

Dans ces torches à plasma connues, l'injection de la poudre dans le plasma s'effectue toujours au-delà de l'extrémité de la torche, c'est-à-dire dans une zone ouverte. Les échanges thermiques entre la poudre et le plasma ne s'effectuent donc pas dans les meilleures conditions possibles. Il en résulte une détérioration rapide des électrodes ainsi qu'une consommation importante de puissance et, par conséquent, un coût d'exploitation élevé.In these known plasma torches, the injection of the powder into the plasma is always carried out beyond the end of the torch, that is to say in an open area. The heat exchanges between the powder and the plasma are therefore not carried out under the best possible conditions. This results in rapid deterioration of the electrodes as well as a significant consumption of power and, consequently, a high operating cost.

Pour la même raison, une partie de la poudre de rechargement n'est pas transférée par le plasma jusqu'au substrat pour assurer le rechargement. Il en résulte qu'une partie de la poudre est perdue et surtout que cette poudre tend à empoussiérer la machine, ce qui conduit à des risques de grippage de celle-ci et complique les opérations d'entretien.For the same reason, part of the recharging powder is not transferred by the plasma to the substrate to ensure recharging. As a result, part of the powder is lost and especially that this powder tends to dust the machine, which leads to risks of seizing thereof and complicates maintenance operations.

La présente invention a précisément pour objet une torche à plasma fonctionnant généralement d'une manière analogue aux torches existantes, tout en ne présentant pas les inconvénients précités. En particulier, l'invention concerne une torche à plasma permettant une amélioration des échanges thermiques entre la poudre et le plasma et créant un rideau gazeux autour du plasma assurant le transfert de la poudre, de façon à diminuer la détérioration des électrodes, à réduire la puissance consommée, à protéger la poudre fondue véhiculée par le plasma et le bain liquide formé sur le substrat contre l'oxydation, et à éviter la propagation de grains de poudre hors de la zone de rechargement.The present invention specifically relates to a plasma torch generally operating in a manner similar to existing torches, while not having the aforementioned drawbacks. In particular, the invention relates to a plasma torch allowing an improvement in the heat exchanges between the powder and the plasma and creating a gaseous curtain around the plasma ensuring the transfer of the powder, so as to reduce the deterioration of the electrodes, to reduce the power consumption, to protect the molten powder conveyed by the plasma and the liquid bath formed on the substrate against oxidation, and to avoid the propagation of grains of powder outside the recharging zone.

A cet effet et conformément à l'invention, il est proposé une torche de rechargement à plasma comprenant, selon un axe commun, une cathode centrale présentant une extrémité effilée, et une anode annulaire entourant la cathode et délimitant avec celle-ci un espace se prolongeant au-delà de l'extrémité effilée de la cathode par un orifice de sortie formé dans l'anode, au moins un passage d'arrivée de poudre de rechargement étant formé dans l'anode et présentant au niveau dudit orifice de sortie une extrémité de sortie inclinée vers ledit axe, caractérisée en ce que l'orifice de sortie présente une partie arrière adjacente à l'espace annulaire et une partie avant débouchant à l'extérieur et de diamètre supérieur au diamètre de la partie arrière, l'extrémité inclinée du passage d'arrivée de poudre de rechargement débouchant dans la partie avant de l'orifice de sortie, des canaux sensiblement parallèles audit axe étant formés dans l'anode autour de la partie arrière de l'orifice de sortie, pour mettre en communication la partie avant de cet orifice avec ledit espace annulaire.To this end and in accordance with the invention, there is provided a plasma recharging torch comprising, along a common axis, a central cathode having a tapered end, and an annular anode surrounding the cathode and delimiting therewith a space extending beyond the tapered end of the cathode by an outlet orifice formed in the anode, at least one inlet passage for recharging powder being formed in the anode and having at one end of said outlet orifice outlet inclined towards said axis, characterized in that the outlet orifice has a rear part adjacent to the annular space and a front part opening out and of diameter greater than the diameter of the rear part, the inclined end of the recharging powder inlet passage opening into the front part of the outlet orifice, channels substantially parallel to said axis being formed in the anode around the rear part of the outlet orifice, to communicate the front part of this orifice with said annular space.

Dans un mode de réalisation préféré de l'invention, cette torche comprend au moins six canaux répartis autour de son axe.In a preferred embodiment of the invention, this torch comprises at least six channels distributed around its axis.

De préférence, la torche comprend également deux passages d'arrivée de poudre disposés symétriquement par rapport à son axe.Preferably, the torch also comprises two powder inlet passages arranged symmetrically with respect to its axis.

On décrira maintenant, à titre d'exemple non limitatif, un mode de réalisation préféré de l'invention en se référant aux dessins annexés dans lesquels :

  • - la figure 1a, déjà décrite, est une vue en coupe longitudinale représentant de façon schématique l'extrémité d'une torche de rechargement à plasma selon la technique antérieure ;
  • - la figure 1b, déjà décrite, est une vue en bout de la torche de la figure 1a ;
  • - la figure 2a est une vue en coupe longitudinale schématique de l'extrémité d'une torche de rechargement à plasma conforme à l'invention ; et
  • - la figure 2b est une vue en bout de la torche de la figure 2a.
A preferred embodiment of the invention will now be described, by way of nonlimiting example, with reference to the appended drawings in which:
  • - Figure 1a, already described, is a longitudinal sectional view schematically showing the end of a plasma recharging torch according to the prior art;
  • - Figure 1b, already described, is an end view of the torch of Figure 1a;
  • - Figure 2a is a schematic longitudinal sectional view of the end of a plasma recharging torch according to the invention; and
  • - Figure 2b is an end view of the torch of Figure 2a.

D'une manière générale, la torche de rechargement à plasma transféré représentée sur les figures 2a et 2b présente une structure voisine de la structure de la torche selon la technique antérieure décrite précédemment en se référant aux figures 1a et 1b. Pour cette raison, les mêmes numéros de référence augmentés de cent sont utilisés pour désigner des éléments analogues.In general, the transferred plasma recharging torch shown in FIGS. 2a and 2b has a structure close to the structure of the torch according to the prior art described previously with reference to FIGS. 1a and 1b. For this reason, the same reference numbers increased by one hundred are used to designate similar elements.

Ainsi, la torche selon l'invention comprend une cathode centrale 110 et une anode annulaire 112 disposées toutes deux selon un axe commun XXʹ.Thus, the torch according to the invention comprises a central cathode 110 and an annular anode 112 both arranged along a common axis XXʹ.

La cathode 110, par exemple en tungstène, a la forme d'une tige cylindrique terminée par une extrémité effilée 110a de forme conique.The cathode 110, for example made of tungsten, has the shape of a cylindrical rod terminated by a tapered end 110a of conical shape.

L'anode 112 présente un alésage cylindrique 113 dans lequel est logée la cathode 110 et délimitant avec cette dernière un espace annulaire 114. Cet espace 114 est utilisé pour injecter le gaz plasmagène, constitué de façon connue soit par de l'argon, soit par un mélange argon-hydrogène, hélium-hydrogène, azote-­ hydrogène, azote-hélium, etc...The anode 112 has a cylindrical bore 113 in which is housed the cathode 110 and delimiting with the latter an annular space 114. This space 114 is used to inject the plasma gas, constituted in a known manner either by argon or by an argon-hydrogen, helium-hydrogen, nitrogen- mixture hydrogen, nitrogen-helium, etc ...

L'alésage cylindrique 113 formé dans l'anode 112 se prolonge au-delà de la pointe de l'extrémité effilée 110a de la cathode, sous la forme d'un orifice de sortie 115 débouchant sur la face plane d'extrémité 116 de l'anode. Cette face 116, perpendiculaire à l'axe XXʹ, forme également l'extrémité de la torche.The cylindrical bore 113 formed in the anode 112 extends beyond the tip of the tapered end 110a of the cathode, in the form of an outlet orifice 115 opening onto the flat end face 116 of the 'anode. This face 116, perpendicular to the axis XXʹ, also forms the end of the torch.

De façon plus précise et conformément à l'invention, l'orifice de sortie 115 comprend une partie arrière 115a raccordée à l'alésage 113 par une partie présentant une section en arc de cercle et une partie avant 115b débouchant sur la face d'extrémité 116. Comme l'illustre la figure 2a, le diamètre de la partie avant 115b est légèrement supérieur au diamètre de la partie arrière 115a, ces deux parties étant séparées par un épaulement droit. De plus, des canaux 122 s'étendant parallèlement à l'axe XXʹ sont formés dans l'anode 112, autour de la partie arrière 115a de l'orifice de sortie, de façon à faire communiquer directement l'espace annulaire 114 avec la partie avant 115b de l'orifice de sortie. Comme l'illustre la figure 2b, ces canaux 122 sont au nombre de six, répartis autour de l'axe XXʹ.More precisely and in accordance with the invention, the outlet orifice 115 comprises a rear part 115a connected to the bore 113 by a part having a circular arc section and a front part 115b opening onto the end face. 116. As illustrated in FIG. 2a, the diameter of the front part 115b is slightly greater than the diameter of the rear part 115a, these two parts being separated by a straight shoulder. In addition, channels 122 extending parallel to the axis XXʹ are formed in the anode 112, around the rear part 115a of the outlet orifice, so as to directly communicate the annular space 114 with the part before 115b of the outlet. As illustrated in Figure 2b, these channels 122 are six in number, distributed around the axis XXʹ.

La poudre de rechargement mélangée au gaz porteur parvient jusqu'à l'extrémité de la torche par deux passages 120 disposés de façon symétrique par rapport à l'axe XXʹ. Ces passages 120, qui s'étendent sensiblement parallèlement à cet axe XXʹ, présentent au niveau de l'orifice de sortie 115 des extrémités 120a inclinées vers l'axe XXʹ et débouchant conformément à l'invention dans la partie avant 115b de cet orifice.The recharging powder mixed with the carrier gas reaches the end of the torch by two passages 120 arranged symmetrically with respect to the axis XXʹ. These passages 120, which extend substantially parallel to this axis XXʹ, have at the outlet orifice 115 ends 120a inclined towards the axis XXʹ and opening out according to the invention in the front part 115b of this orifice.

Grâce à la configuration particulière qui vient d'être décrite, la torche de rechargement à plasma selon l'invention fonctionne de la façon suivante.Thanks to the particular configuration which has just been described, the plasma recharging torch according to the invention operates in the following manner.

Sous l'effet de la tension électrique établie entre la cathode 110 et l'anode 112, le gaz plasmagène admis par l'espace annulaire 114 (flèches F₁) est ionisé pour former un plasma P dans l'orifice de sortie 115, au-delà de la pointe de l'extrémité effilée 110a de la cathode.Under the effect of the electric voltage established between the cathode 110 and the anode 112, the plasma gas admitted by the annular space 114 (arrows F₁) is ionized to form a plasma P in the outlet orifice 115, beyond the tip of the tapered end 110a of the cathode.

Sous l'effet de la différence de potentiel établie entre la torche et le substrat (non représenté), le plasma P est transféré jusqu'au substrat en s'échappant par l'orifice 115.Under the effect of the potential difference established between the torch and the substrate (not shown), the plasma P is transferred to the substrate by escaping through the orifice 115.

Dans la partie avant 115b de l'orifice de sortie 115, la poudre de rechargement véhiculée par le gaz porteur dans les passages 120 (flèches F₂) est injecté directement dans le plasma P. Cette injection s'effectuant dans une zone confinée et non au-­delà de l'extrémité de la torche comme dans la technique antérieure, les échanges thermiques entre la poudre et le plasma sont améliorés. Il en résulte une moindre détérioration des électrodes, une réduction de la puissançe à mettre en oeuvre et, par conséquent, une économie notable.In the front part 115b of the outlet orifice 115, the recharging powder conveyed by the carrier gas in the passages 120 (arrows F₂) is injected directly into the plasma P. This injection takes place in a confined area and not at the beyond the end of the torch as in the prior art, the heat exchanges between the powder and the plasma are improved. This results in less deterioration of the electrodes, a reduction in the power to be used and, consequently, a significant saving.

Simultanément à la formation du plasma P et à l'injection de la poudre de rechargement dans ce plasma, du gaz plasmagène frais et non ionisé est injecté autour du plasma dans la partie avant 115b de l'orifice de sortie, par les canaux 122. On forme ainsi autour du plasma transféré véhiculant la poudre de rechargement un rideau gazeux dynamique schématisé par les flèches F₃ sur la figure 2a.Simultaneously with the formation of the plasma P and the injection of the recharging powder into this plasma, fresh and non-ionized plasma gas is injected around the plasma in the front part 115b of the outlet orifice, through the channels 122. There is thus formed around the transferred plasma carrying the recharging powder a dynamic gaseous curtain shown diagrammatically by the arrows F₃ in FIG. 2a.

Ce rideau gazeux limite la propagation de grains de poudre hors de la zone de rechargement. Il en résulte une augmentation du rendement de la poudre ainsi qu'un moindre empoussièrement des machines. Les risques de grippage de celles-­ci s'en trouvent réduits, de même que le travail d'entretien.This gaseous curtain limits the spread of powder grains outside the recharging area. This results in an increase in the yield of the powder as well as less dust from the machines. The risks of seizure of these are reduced, as well as maintenance work.

Le rideau annulaire gazeux obtenu grâce aux canaux 122 permet de mieux protéger de l'oxydation la poudre fondue entraînée par le plasma P, de même que le bain liquide formé sur le substrat.The gaseous annular curtain obtained thanks to the channels 122 makes it possible to better protect the molten powder entrained by the plasma P from oxidation, as well as the liquid bath formed on the substrate.

Enfin, ce même rideau gazeux assure la protection thermique de la paroi de la partie avant 115b de l'orifice de sortie et réduit également les risques d'accrochage de poudre fondue sur cette même paroi à proximité de la face d'extrémité 116. Par conséquent, la tenue dans le temps de l'anode 112 n'est pas pénalisée par l'allongement de son extrémité nécessitée par l'injection de la poudre de rechargement dans une zone confinée.Finally, this same gaseous curtain provides thermal protection for the wall of the front part 115b of the outlet orifice and also reduces the risk of catching molten powder on this same wall near the end face 116. By Consequently, the resistance over time of the anode 112 is not penalized by the lengthening of its end required by the injection of the recharging powder in a confined area.

Bien entendu, la torche qui vient d'être décrite peut subir différentes modifications sans sortir du cadre de l'invention.Of course, the torch which has just been described can undergo various modifications without departing from the scope of the invention.

Ainsi, l'injection de la poudre de rechargement peut se faire par un passage annulaire dans lequel la poudre circule selon une trajectoire hélicoïdale.Thus, the injection of the recharging powder can be done by an annular passage in which the powder circulates according to a helical trajectory.

En outre, il est clair que le nombre et la forme des canaux 122 peuvent être modifiés, ces canaux pouvant par exemple présenter en section la forme d'arcs de cercle.In addition, it is clear that the number and the shape of the channels 122 can be modified, these channels being able for example to present in section the shape of arcs of a circle.

De plus, les aménagements équipant habituellement les torches de rechargement à plasma et qui n'ont pas été décrits pour simplifier peuvent bien entendu être prévus sur la torche conforme à l'invention. En particulier, des moyens de refroidissement des électrodes, et notamment de l'anode, constitués généralement par une circulation d'un fluide tel que de l'eau peuvent être prévus.In addition, the arrangements usually fitted to plasma recharging torches and which have not been described for simplicity can of course be provided on the torch according to the invention. In particular, means for cooling the electrodes, and in particular the anode, generally consisting of a circulation of a fluid such as water can be provided.

Enfin, bien que l'invention soit particulièrement adaptée à une torche de rechargement à plasma transféré, elle peut aussi s'appliquer à une torche à plasma soufflé.Finally, although the invention is particularly suitable for a reloading torch with transferred plasma, it can also be applied to a blown plasma torch.

Claims (3)

1. Torche de rechargement à plasma comprenant, selon un axe commun (XXʹ), une cathode centrale (110) présentant une extrémité effilée (110a) et une anode annulaire (112) entourant la cathode et délimitant avec celle-ci un espace annulaire (114) d'arrivée de gaz plasmagène, cet espace se prolongeant au-delà de l'extrémité effilée de la cathode par un orifice de sortie (115) formé dans l'anode, au moins un passage (120) d'arrivée de poudre de rechargement étant formé dans l'anode et présentant au niveau dudit orifice de sortie une extrémité de sortie (120a) inclinée vers ledit axe, caractérisée en ce que l'orifice de sortie (115) présente une partie arrière (115a) adjacente à l'espace annulaire (114) et une partie avant (115b) débouchant à l'extérieur et de diamètre supérieur au diamètre de la partie arrière, l'extrémité inclinée (120a) du passage d'arrivée de poudre de rechargement débouchant dans la partie avant (115b) de l'orifice de sortie, des canaux (122) sensiblement parallèles audit axe (XXʹ) étant formés dans l'anode (112), autour de la partie arrière (115a) de l'orifice de sortie, pour mettre en communication la partie avant (115b) de cet orifice avec ledit espace annulaire (114).1. Plasma recharging torch comprising, along a common axis (XXʹ), a central cathode (110) having a tapered end (110a) and an annular anode (112) surrounding the cathode and delimiting with it an annular space ( 114) of plasma gas inlet, this space extending beyond the tapered end of the cathode by an outlet orifice (115) formed in the anode, at least one powder inlet passage (120) of recharging being formed in the anode and having at the level of said outlet orifice an outlet end (120a) inclined towards said axis, characterized in that the outlet orifice (115) has a rear part (115a) adjacent to the annular space (114) and a front part (115b) opening to the outside and of diameter greater than the diameter of the rear part, the inclined end (120a) of the feed powder inlet passage opening into the front part (115b) of the outlet orifice, channels (122) substantially parallel to the said axis (XXʹ) being formed in the anode (112), around the rear part (115a) of the outlet orifice, to put the front part (115b) of this orifice into communication with said annular space (114) . 2. Torche selon la revendication 1, caractérisée en ce qu'elle comprend au moins six canaux (122) répartis autour dudit axe (XXʹ).2. Torch according to claim 1, characterized in that it comprises at least six channels (122) distributed around said axis (XXʹ). 3. Torche selon l'une quelconque des revendications 1 et 2, caractérisée en ce qu'elle comprend deux passages (120) d'arrivée de poudre disposés symétriquement par rapport audit axe (XXʹ).3. Torch according to any one of claims 1 and 2, characterized in that it comprises two passages (120) of powder arrival arranged symmetrically with respect to said axis (XXʹ).
EP87401339A 1986-06-17 1987-06-15 Plasma torch for powder spraying Expired - Lifetime EP0250308B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87401339T ATE56343T1 (en) 1986-06-17 1987-06-15 PLASMA SPRAY TORCH.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8608736 1986-06-17
FR868608736A FR2600229B1 (en) 1986-06-17 1986-06-17 PLASMA RECHARGING TORCH

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EP0250308A1 true EP0250308A1 (en) 1987-12-23
EP0250308B1 EP0250308B1 (en) 1990-09-05

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EP (1) EP0250308B1 (en)
AT (1) ATE56343T1 (en)
DE (1) DE3764725D1 (en)
FR (1) FR2600229B1 (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2636198A1 (en) * 1988-09-08 1990-03-09 Stoody Deloro Stellite Inc NOZZLE FOR PLASMA TORCH AND METHOD FOR INTRODUCING POWDER IN PLASMA TORCH
EP0423370A1 (en) * 1989-03-31 1991-04-24 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Method of treatment with plasma and plasmatron
EP0445147A1 (en) * 1988-11-23 1991-09-11 Plasmacarb Inc Cascade arc plasma torch and a process for plasma polymerization.
EP0461259A1 (en) * 1989-12-26 1991-12-18 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Plasmatron
GR1001021B (en) * 1991-07-17 1993-03-31 Le Politekhn I Im M L Kalinina Air plasma sprayer
GB2300649A (en) * 1995-02-23 1996-11-13 Quigley Associates Powder injection apparatus
WO1999005339A1 (en) * 1997-07-28 1999-02-04 Volkswagen Aktiengesellschaft Method for thermal coating, especially for plain bearings
WO2001032949A1 (en) * 1999-10-30 2001-05-10 Agrodyn Hochspannungstechnik Gmbh Method and device for plasma coating surfaces
US6379754B1 (en) 1997-07-28 2002-04-30 Volkswagen Ag Method for thermal coating of bearing layers
WO2004028222A1 (en) * 2002-09-18 2004-04-01 Volvo Aero Corporation A thermal spraying device
US7557324B2 (en) 2002-09-18 2009-07-07 Volvo Aero Corporation Backstream-preventing thermal spraying device
EP2676735A4 (en) * 2011-07-12 2015-05-06 Shinwa Industry Co Ltd Axial feed plasma spraying device
WO2019166473A1 (en) * 2018-02-27 2019-09-06 Oerlikon Metco Ag, Wohlen Plasma nozzle for a thermal spray gun and method of making and utilizing the same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011177743A (en) * 2010-03-01 2011-09-15 Honda Motor Co Ltd Plasma welding torch and welding method using plasma welding torch

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US3148263A (en) * 1961-08-02 1964-09-08 Avco Corp Plasma-jet torch apparatus and method relating to increasing the life of the downstream electrode
US4127760A (en) * 1975-06-09 1978-11-28 Geotel, Inc. Electrical plasma jet torch and electrode therefor

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US3148263A (en) * 1961-08-02 1964-09-08 Avco Corp Plasma-jet torch apparatus and method relating to increasing the life of the downstream electrode
US4127760A (en) * 1975-06-09 1978-11-28 Geotel, Inc. Electrical plasma jet torch and electrode therefor

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2636198A1 (en) * 1988-09-08 1990-03-09 Stoody Deloro Stellite Inc NOZZLE FOR PLASMA TORCH AND METHOD FOR INTRODUCING POWDER IN PLASMA TORCH
EP0445147A1 (en) * 1988-11-23 1991-09-11 Plasmacarb Inc Cascade arc plasma torch and a process for plasma polymerization.
EP0445147A4 (en) * 1988-11-23 1992-01-15 Plasmacarb Inc. Cascade arc plasma torch and a process for plasma polymerization
EP0423370A1 (en) * 1989-03-31 1991-04-24 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Method of treatment with plasma and plasmatron
EP0423370A4 (en) * 1989-03-31 1991-11-21 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Method of treatment with plasma and plasmatron
EP0461259A1 (en) * 1989-12-26 1991-12-18 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Plasmatron
EP0461259A4 (en) * 1989-12-26 1992-12-30 Leningradsky Politekhnichesky Institut Imeni M.I.Kalinina Plasmatron
GR1001021B (en) * 1991-07-17 1993-03-31 Le Politekhn I Im M L Kalinina Air plasma sprayer
GB2300649A (en) * 1995-02-23 1996-11-13 Quigley Associates Powder injection apparatus
GB2300649B (en) * 1995-02-23 1998-07-22 Quigley Associates Improvements in thermal spraying apparatus
WO1999005339A1 (en) * 1997-07-28 1999-02-04 Volkswagen Aktiengesellschaft Method for thermal coating, especially for plain bearings
US6379754B1 (en) 1997-07-28 2002-04-30 Volkswagen Ag Method for thermal coating of bearing layers
WO2001032949A1 (en) * 1999-10-30 2001-05-10 Agrodyn Hochspannungstechnik Gmbh Method and device for plasma coating surfaces
US6800336B1 (en) 1999-10-30 2004-10-05 Foernsel Peter Method and device for plasma coating surfaces
WO2004028222A1 (en) * 2002-09-18 2004-04-01 Volvo Aero Corporation A thermal spraying device
US7557324B2 (en) 2002-09-18 2009-07-07 Volvo Aero Corporation Backstream-preventing thermal spraying device
EP2676735A4 (en) * 2011-07-12 2015-05-06 Shinwa Industry Co Ltd Axial feed plasma spraying device
WO2019166473A1 (en) * 2018-02-27 2019-09-06 Oerlikon Metco Ag, Wohlen Plasma nozzle for a thermal spray gun and method of making and utilizing the same

Also Published As

Publication number Publication date
FR2600229A1 (en) 1987-12-18
ATE56343T1 (en) 1990-09-15
FR2600229B1 (en) 1994-09-09
DE3764725D1 (en) 1990-10-11
EP0250308B1 (en) 1990-09-05

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